Experimental study of sodium reignition behavior

Ohno, Shuji  ; not registered ; not registered; not registered  ; not registered 

Reaction residue of sodium combustion has possibility of reignition in an air atmosphere even at 50C when the sodium pool fire was extinguished by nitrogen (N) gas. Thus we carried out an experimental study of this behavior for the purpose to clarify the cause of the reignition and to make a suggestion for a preventive measure. The sodium burning and extinguishing experiments were performed changing fraction of oxygen (O), carbon-dioxide (CO) and humidity in the atmosphere, using 1g sodium and a glass-made chamber of 70mm inner diameter and 300mm length. By the observation of phenomena, measurement of reignition temperature, and analyses of reaction residue, the following results and conclusions were obtained. (1)When the burning was distinguished by pure N gas, reignition did not occur at 59C. However, reignition occurred at 50C when the distinguishing N gas contained over 1% O. (2)Reignition temperature became higher by supplying humidity and CO after cooling down the residue, even when the distinguishing N gas contained O. (3)The reaction residue consisted mainly of NaO and Na, partly of NaOH, NaCO, and NaO depending on the experimental condition. No peculiar compound was detected. The reignition might be attributed to the sharply projecting-shaped gray-white-colored reaction products which contains NaO.